Rotary pump or expansion engine



Dec. 28, 1954 KAI BORGE MOSSIN 2,698,130

ROTARY PUMP OR EXPANSION ENGINE Filed March 2, 1949 2 Sheets-Sheet l 2 INVENTOR.

28, 1954 KAI BORGE MOSSIN 2,693,130

ROTARY PUMP OR EXPANSION ENGINE Filed March 2, 1949 2 Sheets-Sheet 2 INVEN TOR.

United States Patent M 2,698,136 ROTARY PUMP 0R EXPANSION ENGINE Kai Bdrge. Mossin, Hellerup, Denmark, assignor to Novo Ter'apeutisk Laboratoriuin A/ S, Gop'enhagen, Denmark aspirates March *2, 1919, Serial 715,127

The invention relates to rotary volumetric displacement machines which can be used in general either as pumps or compressors, or as expansion engines.

Rotary pumps or blowers of the so-cal-led rotary im-- peller type are known which have two members or impellers rotating in a casing, and in which the casing in cross section has the form of two equally large cylinders intersecting each other. By way of example, the Ro'ots blower as shown, e. g. in United States Patent 1,746,885, has two equal rotors of substantially S-shaped cross section so that each rotor has two lobes. D'uring rotation, one of the rotors is in constant linear contact with the surrounding cylinder by one of its lobes while its other lobe maintains linear contact with the other rotor.

In a modification of this type of machine, which can be used. as a pump or as an engine, one rotor has a single lobe and the other has three lobes and is driven at one-third the speed of the first.

Such machines suffer from the drawback that the clearance or dead space is considerably larger than is the case with an ordinary reciprocating machine having pistons working in cylinders.

The object of the present invention is to construct a machine of the kind referred to having a very small such clearance, and which can be used either as a rotary pump *or as an expansion engine. When used as pump or compressor, the compression is effected uniformly, almost as is the case in a reciprocating machine and to the compression ratio desired. The compression rate may, if desired, be altered during the operation of the machine.

If the machineaccording to 'the invention is used "as-an expansion engine, the two rotors will be brought to rotate by means of the expansion of a pressure medium, e. g. atmospheric air, a gas, or a vapour, the expansion occurring uniformly almost as in the case in a reciprocating steam engine and to the expansion ratio desired. The expansion ratio may, if desired, be varied dur ing theoperation of the'expan'sion engine.

Further objects and advantages of the invention will be apparent from the following description with referenceto the drawingsin which:

Figs. '1 to 3 are cross sections through arotary pump with the two rotors in three difliere'nt positions in relationlto each other,

Figs. 4 to '6 are diagrammatic cross sections through the upper, half of another form of rotary pump, "likewise showing the two rotors of the pump in thr'ee different positions in relation to "each other, and

Fig. 7 is a cross section similar to Fig. 1 but with a modified valve arrangement in the exhaust channel.

1 in Fig. 1 designates the casing of the pump, said casing having internally the form 'of two cylind'ers '2 and that partly intersect each other. A =suction=channel 4 terminates in a suction opening 5 which in the drawing is shojwnfleading into the cylinder "2, :but may as well lead into the cylinder 3,0r to the transition between the two cylinders 2 and 3. -An exhaust opening 6 which in the casing l is placed wholly or substantially opposite to the suction opening 5, and which may be provided in one of the cylinder-sat the transition between the latter, leads to an exhaust channel '7. In 'the cylinder 2, a rotor 9 is mounted on arotary shaft 10, the axis/11 of 'which coincides with the axis of the cylinder 2. The rotor -9ihas only one, lobe, -i. e. only'one-line 2031011}; which it can touch ;-the cylinder =2 *during the rotation. In Fig. 3 it has, however, by thedouble'arrow Patented Dec. 28, 1954 been indicated that the lobe on the rotor 9 may be shaped so that it can touch the cylinder 2 with 'a contact face of a rather considerable width. The shaft 10 lies eccentrically in relation to the rotor 9, and the latter is so shaped that the geometrical center of its cross see tion is separate from the axis of rotation 11 of the rotor. The cross section of the rotor 9 will as a rule be exactly or approximately circular but it can also be otherwise shaped, for instance approximately cardioid shaped. In the cylinder 3 a rotor 12 is mounted on a rotary shaft 13, the axis 14 of which is concentric with the cross section of the rotor 12.

As appears particularly from Fig. 2, during rotation the rotors 9 and 12 touch each other along a single line. The rotor 12 has an approximately triangular cross section and thereby three lobes, so that the rotor 12 can touch the enclosing cylinder along three contact lines.

The rate of revolution of the multi-lobe rotor 12 is equal to the rate of revolution for the single-lobe rotor 9 divided by a whole number equal to the number of lobes inone rotor to that in the other and greater than 1-. As the rotor 9 has one lobe while the rotor 12 :has three lobes, the rotor 9 will turn a full revolution for every third of a revolution of the rotor 12. The directions of rotation of the two rotors 9 and 12 are indicated with arrows in Figs. 1 3.

In the exhaust channel 7 of the pump there is a valve arrangement consisting of a rotary valve. This rotary valve is formed by a cylinder 23 which rotates at a rate of revolution corresponding to half the rate of revolution of the fast-running rotor 9 of the pump. In the cylinder 23, the direction of rotation of which is indicated with an arrow, there is a cross-channel 24 which during the rotation of the cylinder will alternately open and close the exhaust channel 7.

Fig. 1 shows the two rotors 9 and 12 in the position in relation to each other which they will assume at a point when the fast running ro'tor 9 has just closed the suction opening 5 with the result that in the cylinder 2 a fluid volume 15 will be cut off which has flowed in through the suction opening before it was 'closed. Another fluid volume llfip'reviously admitted through the suction opening 5 has by this time been transported by the slow-running rotor 12 to the vicinity 'of the exhaust opening 6, as appears from Fig. "1. h

Fig. 2 shows the position of the two rotors 9 and 12 after the fast-running rotor 9 has turned about from 'the position shown in Fig. 1. The two volumes 15 and 16 in Fig. 1 will in Fig. 2 be seen to 'be united, and this union has taken place a short time after the closing of the suction opening by the fast-running rotor and under compression. The total volume is in Fig. -2 designated by 17, and the atmospheric air, 'ga's, vapor, or other medium that the pump is to compress, has in Fig. 2 been compressed to about half of its original volume.

The valve 23 in the exhaust channel is :just =commencing to open.

Fig. 3 shows the rotors 9 and 12 in positions corresponding to the fast-running rotor having turned a further from the position shown in Fig. 2. Theipurnp has now discharged practically the entire volume 17 of Fig. 2 through exhaust channel 7, and the valve 23 is on the point of closing. The'clearance of the'pump is-designated by 18 in Fig. 3.

It appears from Fig. 3 that the clearance '18 can become less if the two rotors 9 and '12 can be turned closer together without it being possible for the compressedthe pressure chamber of the pump from entering the suction chamber '19 in-the cylinder 2, Fig. 3.

Figs. 4-6 show diagrammatically that a *pump in accordance with the invention may-be built with two rotors 21 and 22, of which'the rotor -21-has o'nly-onelobe an'd substantially-corresponds to the rotor9in Figs. 1-3, while r the other rotor 22 is made with two lobes. The rotor 22 is rotated at a rate of revolution that is half the rate of revolution of the rotor 21. Otherwise the rotary pump in accordance with Figs. 46 operates in practically the same way as the pump shown in Figs. 1-3, which will be seen by comparing Fig. 4 to Fig.1, Fig. 5 to Fig. 2, and Fig. 6 to Fig. 3.

The suction opening and the exhaust opening in the pump shown in Figs. 4-6 may be mounted in the same way as the corresponding openings in Figs. 1-3.

In the case where the single-lobe rotor 9 in Figs. l-3 or 21 in Figs. 4-6 deviates from the circular cross section by being provided with a rather wide contact surface against the cylinder as indicated by the double arrow 120 in Fig. 3, the two rotors will during the rotation be in contact with each other along a single line apart from a short period at the termination of the compression and at the commencement of the suction. These short periods are symmetrically disposed with relation to the connection line between the axes of rotation of the two rotors. In said two short periods the single-lobe rotor 9 or 21 will with the flattened part indicated with the double arrow 120 in Fig. 3 have contact with the multilobe rotor 12 or 22 along two or more different lines, between which an imperceptibly small volume is enclosed which is conveyed from the pressure side to the suction side, but which imperceptibly small volume may be completely disregarded. By a special forming of the transitions between the flattened part and the remaining surface of the single-lobe rotor there will, however, be a possibility of avoiding said conveyance of an imperceptibly small volume of the pressure medium from the pressure side of the pump to the suction side.

The object of the modified exhaust valve shown in Fig. 7 is to permit variation of the compression of the pump during the operation.

In Fig. 7, corresponding parts have been designated by the same reference numbers as in Fig. 1. Around the outside of the rotary valve or cylinder 23 there is a bipartite tube 25, 26 which forms a bearing for the rotary valve. At least the tube part can be turned, so that the edge 27 of said tube part 25 adjacent to the pump casing is moved into the exhaust channel as indicated in Fig. 7. Hereby is attained that the point for the opening of the rotary valve may be varied, so that the exhaust through the channel 7 does not begin until the pressure in the pump has reached a certain height. It would be possible to make the valve 23 rotate in the opposite direction to that indicated by the arrow in Fig. 7. In such a case the adjustment arrangement would involve the tube part 26, the edge of which adjacent to the pump casing 1 would be turned into the exhaust channel 7 with the result that the point for the opening of the rotary valve would be varied.

As exemplified above, the rotary pump in accordance with the invention may, as shown in Figs. 4-6, have a slow-running rotor with two lobes or, as shown in Figs. 1-3 and in Fig. 7, it may have a slow-running rotor with three lobes. It could also have four or more lobes, but more than four lobes 0n the slow-running rotor will scarcely be of any practical interest, as it would unduly increase the size of the slow-running rotor.

The rotary valves with pertaining adjustment arrangements as described can be used in pumps in accordance with the invention with a slow-running rotor having more or less than three lobes. Above it has been explained how the machine functions as a rotary pump. When used as an expansion engine driven by atmospheric air, gas, or vapour under pressure, said fluid is admitted through the channel above described as the exhaust channel of the pump and discharged, after expansion, through the channel above termed the suction channel of the pump. The operation will be the opposite to that described above, and the rotors will rotate in the directions opposite to those indicated by arrows in the drawing.

The volume enclosed between the rotors 9 and 12 will further expand while at the same time work is yielded to the rotors. The machine will, in order, as an expansion engine function in just the opposite way to that in which the engine functions when ,used as rotary pump. The valve adjustment arrangement which, when the machine functions as a pump, is used for determining the exhaust pressure of the pump, will, when the machine is used as an expansion engine, act to vary the amount of pressure fluid admitted to the machine.

When the machine is used as an expansion engine, i. e. as a power engine, it will not be possible to start it in all positions of the rotors. This disadvantage can be eliminated by combining several expansion engines in such a way that they operate with common supply and exhaust pipes. Hereby can be attained that one of the engines will always have its rotors in starting position. In a similar way it will also be possible to combine several rotary pumps in accordance with the invention.

I claim:

1. A rotary volumetric displacement machine having in combination, a casing enclosing a working space having the cross-sectional shape of two intersecting circles, a first rotor of circular cross-sectional shape and journalled for rotation about an axis off-set in relation to the geometrical centre of the cross-sectional area of the rotor, a second rotor having at least two teeth and journalled for rotation about an axis through the centre of the cross-sectional area of said second rotor, a driving connection between said two rotors causing the second rotor to revolve in operation in the opposite direction from that of the first rotor and with a rotational speed equal to the rotational speed of the first rotor divided by the number of teeth of the second rotor, the crosssectional shapes of the two rotors being interrelated in such manner as to establish, at any stage of the operation, contact between the rotors at least along a single line, inlet and outlet ducts for the working medium communicating with the working space and opening into the working space in the vicinity of the points of intersection of the two circles defining the cross-sectional shape of the working space, a rotary valve disposed in close proximity to the working space in the duct, in which the highest medium pressure prevails during operation, and means for driving said rotary valve in properly timed relation with the rotors.

2. In a rotary volumetric displacement machine as claimed in claim 1, the said rotary valve comprising a cylindrical valve body having a through transverse duct, and an adjustable regulating device in conjunction with said valve body for adjusting the timing of one of the operational functions of said valve body.

3. In a rotary volumetric displacement machine as claimed in claim 1, the cross-sectional shape of the multitoothed rotor between consecutive teeth being substantially concave and approximately that of an arc of a circle having substantially the same radius as the cooperating portion of the other rotor and its centre lying upon the bisector of the angle between said consecutive teeth.

4. In a rotary volumetric displacement machine as claimed in claim 3, the multi-toothed rotor comprising three teeth, the tips of which have approximately the cross-sectional shape of outward convex semi-arcs of a circle having its centre on a line through the centre of the Irotor and the outermost point of the tip of each toot 5. A rotary volumetric displacement machine having in combination, a casing enclosing a working space having the cross-sectional shape of two intersecting circles, a first rotor of circular cross-sectional shape and jour nalled for rotation about an axis off-set in relation to the geometrical centre of the cross-sectional area of the rotor, a second rotor having three teeth and journalled for rotation about an axis extending through the center of the cross-sectional area of said second rotor, the crosssectional shape of the three-toothed rotor between consecutive teeth being that of an arc of a circle having substantially the same radius as the cooperating portion of the first rotor, the tips of the teeth having approximately the cross-sectional shape of outward convex semi-arcs of a circle having its center on a line extending radially through the center of the second rotor, a driving connection between said two rotors causing the second rotor to revolve in operation in the opposite direction from that of the first rotor and with a rotational speed equal to the rotational speed of the first rotor divided by the number of teeth of the second rotor, the cross-sectional shapes of the two rotors being interrelated in such manner as to establish, at any state of the operation, contact between the rotors at least along a single line, in-.

let and outlet ducts for the working medium communieating with the working space and opening into the working space in the vicinity of the points of intersection of the two circles defining the cross-sectional shape of the working space, a rotary valve disposed in close proximity to the working space in the duct, in which the highest medium pressure prevails during operation, and means for driving said rotary valve in properly timed relation with the rotors.

6. A rotary volumetric displacement machine having in combination, a casing enclosing a working space having the cross-sectional shape of two intersecting circles, a first rotor of a cross-sectional shape closely approaching a circle and journalled for rotation about an axis offset in relation to the geometrical center of the cross-sectional area of the rotor, a second rotor having three teeth and journalled for rotation about an axis extending through the center of the cross-sectional area of said second rotor, the cross-sectional shape of the threetoothed rotor between consecutive teeth being that of an arc of a circle having substantially the same radius as the cooperating portion of the first rotor, the tips of the teeth having approximately the cross-sectional shape of outward convex semi-arcs of a circle having its center on a line extending radially through the center of the second rotor, a driving connection between said two rotors causing the second rotor to revolve in operation in the opposite direction from that of the first rotor and with a rotational speed equal to the rotational speed of the first rotor divided by the number of teeth of the second rotor, the cross-sectional shapes of the two rotors being interrelated in such manner as to establish, at any state of the operation, contact between the rotors at least along a single line, inlet and outlet ducts for the working medium communicating with the working space and opening into the working space in the vicinity of the points of intersection of the two circles defining the cross-sectional shape of the working space, a rotary valve disposed in close proximity to the working space in the duct, in which the highest medium pressure prevails during operation, and means for driving said rotary valve in properly timed relation with the rotors.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Re. 22,818 Berry Dec. 17, 1946 165,805 Disston July 20, 1875 730,679 Monroe June 9, 1903 1,037,455 Diefenderfer Sept. 3, 1912 1,098,256 Harper May 26, 1914 1,432,081 Mitchell Oct. 17, 1922 1,746,885 Bunge et a1 Feb. 11, 1930 1,771,863 Schmidt July 29, 1930 1,953,695 Walter Apr. 3, 1934 FOREIGN PATENTS Number Country Date 2,866 Great Britain 1899 458,408 France Aug. 6, 1913 604,302 France Jan. 25, 1926 653,903 France Nov. 19, 1928 

